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Genome-wide characterization of DNMT-deficient mouse ESCs reveals dynamicity of differentially-methylated-regions and its impact on bivalency composition

ABSTRACT: Differentially-methylated-regions (DMRs), pivotal to the diagnosis/pathogenesis of imprinting disorders, control imprinted gene expression with histone modifications; however, their establishment, numbers, boundaries, and crosstalk with chromatin remain elusive. Herein our global profiling reveals that although de novo methyltransferases DNMT3a/3b are required for locus-specific DMR maintenance, DNMT1 is required for all known DMRs. Based on the latter and the DMR concept, we have developed two novel approaches, “no restored DMRs (NORED)” and “Tag-mosaicity,” to identify/demarcate 31 known and 7 novel DMRs from 21 known loci, and 20 novel DMRs from novel loci. Tag-mosaicity analyses reveal the expected bimodal patterns of hypo/hypermethylated tags of known and new DMRs. Using Gtl2 locus, we demonstrate that methylation of DMRs controls H3K9me3 distribution to a long- range ”DMR-territory” that extends beyond our defined DMR boundary. These findings contrast that H3K9me3 controls CG methylation in Arabidopsis and Neurospora. Our analyses reveal that promoters of imprinted genes within a DMR-territory tend to have H3K4me2 and H3K9me3 with/without H3K27me3, whereas promoters outside have H3K27me3 and H3K4me2. Lastly, we confirmed that the transient DMR of Hcn2/Polrmt locus is conserved in the human genome. Our data link transient DMRs to epilepsy and chronic pain, Parkinson’s disease, Charcot-Marie-Tooth disease, and type 2 diabetes.

ORGANISM(S): Mus musculus

PROVIDER: GSE61648 | GEO | 2016/09/15

SECONDARY ACCESSION(S): PRJNA261744

REPOSITORIES: GEO

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Project description:Genomic imprinting is a mechanism in which the expression of genes varies depending on their parent-of-origin. Imprinting occurs through differential DNA methylation and histone modifications on the two parental alleles, with most imprinted genes marked by CpG-rich differentially methylated regions (DMRs). DNA methylation profiling in cases of uniparental disomy (UPD) provides a unique system permitting the study of DNA derived from a single parent (PMID: 20631049). Approximately 70 human imprinted genes have been described, and imprinted loci have been associated with diseases such as diabetes and cancer. We profiled parent of origin DNA methylation marks to find novel imprinted loci. Methods: We have an unprecedented collection of whole blood DNA from XX patients with UPD covering 18 different chromosomes, allowing for the efficient detection of DMRs associated with imprinted genes for 84% of the human genome. Our study is complimented with Ovarian Teratoma DNA (maternal DNA) and Complete hydatidiform Mole (paternal DNA). DNA methylation was profiled using Illumina Infinium 450K Methylation BeadArrays. Imprinted DMRs were defined by sites at which the maternal and paternal methylation levels diverged significantly from the biparental average. We confirmed novel DMRs by bisulfite sequencing of informative trios and SequenomEpiTYPER assays. Allelic specific gene expression studies were also performed by RNA sequencing in independent biparental controls. Findings: Our results provide for the first comprehensive map of the human imprintome, doubling the number of known imprinted regions. We identified a total of 71 DMRs, 41 of which were novel. 27 novel DMRs were maternally methylated and 14 were paternally methylated. We identified DMRs on chromosomes 5, 21 and 22 previously considered devoid of imprinting, highlighting potential parent-of-origin effects in chromosomal aneuploidies such as Down syndrome. We also found DMRs in genes associated with Schizophrenia and epilepsy. Interpretation: Our data provide the first comprehensive genome-wide map of imprinted sites in the human genome, and provide novel insights into potential parent-of-origin effects in human disorders. 66 UPD samples analyzed in total, From each individual, whole bllod DNA was extracted and global DNA methylation levels were assessed using Illumina Infinium HumanMethylation450 BeadChip.

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Genome-wide characterization of DNMT-deficient mouse ESCs reveals dynamicity of differentially-methylated-regions and its impact on bivalency composition

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